| As a typical representative of Lepidopteran insects, the silkworm, Bombyx mori, has numerous advantages, such as simple husbandry, highly prolific reproduction and short generation, easily handled with moderate body size, clear genetic background and abundant mutation resources. Silkworm has not only been studied in the genetic fields, but also been used as a new experimental animal model of human disease and drug screening. Living longer is the same dream of all people. The health protection medicines in the market attract people’s attention by the flags of “lifespan extension”. In such great wave within irregular mixed are inevitable. It is indispensable using animal models for rapid evaluation of efficacy. Astragalus membranaceus is one of most famours tonic. In recent years, some studies have shown that Astragalus polysaccharide(APS) could prolong lifespan, however its molecular mechanisms remain unknown.In this study, to promote the process of silkworm as a model animal for medicine efficacy evaluation, we detected the effect of APS on lifespan in silkworms and its molecular mechanism. This work investigated physiological parameter(including body weight, food intake, fecundity and lifespan), antioxidant capacity, and immunity effects of APS in silkworm. Then we tested the expression level of the crucial gene of endoplasmic reticulum stress(ERS) in vivo and in vitro after APS treated. Based on this study, the molecular mechanism of APS extending the silkworm lifespan was preliminarily analyzed and speculated. The main results are as follows:1. The effects of APS on lifespan and physiological parameter of silkworm This work investigated the effects of APS on lifespan and physiological parameter of the silkworm. The results showed that the mean lifespan and the maximum lifespan expectancy of female silkworm treated with APS were significantly longer than control group. Meanwhile, the average body weight of both sexes treated with APS were significantly more than control group. There were no significant difference in food intake and fecundity between the two groups. Collectively, our results indicate that dietary APS supplementation could improve the growth performance and extend the lifespan of silkworm.2. The effects of APS on antioxidative capacity of silkworm. The antioxidant enzyme activity were assayed in the 5th instar larvae between APS treated and control group. APS upregulated the superoxide dismutase(SOD) and glutathione S-transferase(GST) activity. However, APS treated group had no effect observed on MDA levels.3. The effects of APS on immunity of silkworm We investigated the effects of APS on the content of main innate immune parameters of silkworm. The dietary APS supplementation caused a significant increased in the Lysozyme(Lys) content in the blood of 5th instar larvae, but there was no significant difference of Antibacterial peptide(Att) content between the two groups. Furthermore, we analysed the timepoint of deaths of silkworm after pathogenic bacteria infection, and in this way to compare the comprehensive immune capacity between APS treated group and control. The dietary APS supplementation significantly increased in resistance to pathogenic microorganisms. All these results suggested that APS upregulated the immunity of silkworm.4. The influence of APS on ERS of silkworm There is a close relationship among ERS, aging process, antioxidant capacity, and immunity. Based on previous researches, we hypothesized that APS maybe have the ability to regulate ERS. The APS significantly relieved the ERS in vitro and in vivo. This results suggested that APS had the ability to decrease the ERS and balance the ER homeostasis.From all the results shown above, we speculated that APS might extend the lifespan of silkworm by decreasing the ERS, enhancing antioxidative capacity and immunity. Silkworm as the experimental animal model for evaluating the Chinese berb pharmacodynamics is short period and low-cost. It has the potentiality to be a drug screening model. |
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